Marriage

As a general rule, I would contend that if something is morally wrong, then it should be possible to present non-fallacious and reasonable arguments to show that it is wrong. I would also probably add that there should be actual facts involved. I would obviously not claim that the arguments must be decisive—one generally does not see that in ethics. While people continue to argue against same sex marriage, the arguments continue to be the usual mix of fallacies and poor reasoning. There is also the usual employment of “facts” that are often simply not true.

In the United States, the latest battle over same-sex marriage is taking place in Utah. The state is being sued on the grounds that the amendment that forbids same-sex marriage is a violation of their rights. The lawsuit certainly has merit—a state does not get to violate constitutional rights even if many people vote in favor of doing so. As such, a rather important legal question is whether or not same-sex couples’ rights are violated by this law.

Utah is following the usual model of arguing against same-sex marriage, although they have at least not broken out the argument that allowing same-sex marriage will lead to or is equivalent to a person marrying a goat.

As might be expected, they made used of the usual pair of fallacies: appeal to tradition and appeal to common practice by claiming that defining marriage as being between a man and a woman is correct because it is “age-old and still predominant.”

Utah also tried the stock procreation gambit, with an added bit about the state’s interest: “Same-sex couples, who cannot procreate, do not promote the state’s interests in responsible procreation (regardless of whether they harm it).” Utah has also made use of the boilerplate argument about “responsible procreation” and “optimal mode of child rearing.”

Same-sex marriage is thus criticized on two grounds in regards to “responsible procreation.” The first is that same-sex couples cannot procreate naturally. The second is that same-sex couples will fail to provide an “optimal mode of child rearing.” To deny same-sex couples the right to marry because of these criticisms would require accepting two general principles: 1) marriage is to be denied to those who do cannot or do not procreate and 2) people who are not capable of the “optimal mode of child rearing” are to be denied marriage.

The first principle entails that straight couples who do not want children or cannot have them must also be denied marriage. After all, if an inability (or unwillingness) warrants denying same-sex couples the right to marry, the same would also apply to different-sex couples.

This principle would also seem to imply that couples who use artificial means to reproduce (such as in vitro fertilization or a surrogate) must be denied marriage. After all, same-sex couples can use these methods to procreate. Alternatively, if different-sex couples can use these methods and be allowed to marry, then same-sex couples who procreate would thus also be entitled to marriage.

The principle would also seem to entail that all married couples would be required to have at least one child, presumably within a specific time frame to ensure that the couple is not just faking their desire (or ability) to have children in order to get married. This would certainly seem to be a violation of the rights of the parents and a rather serious intrusion of the state.

The second principle would entail that straight couples who are not optimal parents must be denied marriage. This would seem to require that the state monitor all marriages to determine that the parents are providing an optimal mode of child rearing and that it be empowered to revoke marriage licenses (much like the state can revoke a driver’s license for driving violations) for non-optimal parents. Different-sex parents can obviously provide non-optimal modes. After all, child abuse and neglect are committed by different-sex couples.

While I do agree that irresponsible people should not have children and that the state has an obligation to protect children from harm, it seems absurd to deny such people the right to marry. After all, not allowing them to marry (or dissolving the marriage when they proved irresponsible) would hardly make such people more responsible or benefit the children. Now to the matter of the state’s interest.

For the sake of the argument, I will grant that the state has an interest in having people reproduce. After all, the state is just a collection of people, so if there are no new people, the state will cease to exist. Of course, this also would seem to give the state an interest in immigration—that would also replace lost people.

This interest in procreation does not, however, entail that the state thus has an interest in preventing same sex-marriage. Allowing same-sex marriage does not reduce the number of different-sex marriages—that is, there is not a limited number of allowed marriages that same-sex couples could “use up.” Also, even if there were a limited number of allowed marriages, same-sex couples would only be a small percentage of the marriages and, obviously enough, marriage is not a necessary condition for procreation nor responsible procreation. That is, people can impregnate or be impregnated without being married. People can also be good parents without being married.

In light of these arguments, the procreation argument against same-sex marriage is still clearly absurd.

While same-sex marriage seems to have momentum in its favor in the United States, there is still considerable opposition to its acceptance. This opposition is well stocked up with stock arguments against this practice. One of these is the slippery slope argument: if same-sex marriage is allowed, then people will then be allowed to marry turtles, dolphins, trees, cats, corpses or iPads. Since this would be bad/absurd, same-sex marriage should not be allowed. This is, of course, the classic slippery slope fallacy.

This is a fallacy in which a person asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question. In most cases, there are a series of steps or gradations between one event and the one in question and no reason is given as to why the intervening steps or gradations will simply be bypassed. This “argument” has the following form:

This sort of “reasoning” is fallacious because there is no reason to believe that one event must inevitably follow from another without adequate evidence for such a claim. This is especially clear in cases in which there are a significant number of steps or gradations between one event and another.

In the case of same-sex marriage the folks who claim these dire results do not make the causal link needed to infer, for example, that allowing same-sex marriage will lead to people marrying goats. As such, they are committing this fallacy and inviting others to join them in their error.

While I have written a reply to this fallacious argument before, hearing someone making the argument using goat marriage and corpse marriage got me thinking about the matter once again.

Using goat marriage as an example, the idea is that if same-sex marriage is allowed, then there is no way to stop the slide into people marrying goats. Presumably people marrying goats would be bad, so this should be avoided. In the case of corpse marriage, the gist is that if same-sex marriage is allowed, then there would be no way to stop the slide into people marry corpses. This would presumably be bad and hence must be avoided.

The slide down the slippery slope, it must be assumed, would occur because a principled distinction cannot be drawn between humans and goats. Nor can a principled distinction be drawn between living humans and corpses. After all, if such principled distinctions could be drawn, then the slide from same-sex marriage to goat marriage and corpse marriage could be stopped in a principled way, thus allowing same-sex marriage without the alleged dire consequences.

For the slippery slope arguments to work, there must not be a way to stop the slide. That is, there is a smooth and well-lubricated transition between humans and goats and between living humans and corpses. Since this is a conceptual matter rather than a matter of actual slopes, the slide would go both ways. That is, if we do not have an adequate wall between goats and humans, then the wall can be jumped from either direction. Likewise for corpses.

So, for the sake of argument, let it be supposed that there are not such adequate walls—that once we start moving, we are over the walls or down the slopes. This would, apparently, show that same-sex marriage would lead to goat marriage and corpse marriage. Of course, it would also show that different sex-marriage would lead to a slide into goat marriage and corpse marriage (I argued this point in my book, For Better or Worse Reasoning, so I will not repeat the argument here).

Somewhat more interestingly, the supposition of a low wall (or slippery slope) between humans and animals would also lead to some interesting results. For example, if we allow animals to be hunted and there is no solid wall between humans and animals in terms of laws and practices, then that would put us on the slippery slope to the hunting of humans. So, by the logic of the slippery slope, we should not allow humans to hunt animals. Ditto for eating animals—after all, if same-sex marriage leads to goat marriage, then eating beef must surely lead to cannibalism.

In the case of the low wall (or slippery slope) between corpses and humans, then there would also be some odd results. For example, if we allow corpses to be buried or cremated and there is no solid wall between the living and the dead, then this would put us on the slippery slope to burying or cremating the living. So, by the logic of the slippery slope, we should not allow corpses to be buried or cremated. Ditto for denying the dead the right to vote. After all, if allowing same-sex marriage would warrant necrophilia, then denying corpses the vote would warrant denying the living the right to vote.

Obviously, people will want to say that we can clearly distinguish between animals and humans as well as between the living and corpses. However, if we can do this, then the slippery slope argument against same-sex marriage would lose its slip.

One of the many stock fallacious arguments against same sex-marriage is the slippery slope argument in which it is contended that allowing same sex-marriage will lead to allowing polygamous marriage (or at least bigamy). The mistake being made is, of course, that the link between the two is not actually made. Since the slippery slope fallacy is a fallacy, this is obviously a bad argument.

A non-fallacious argument that is also presented against same sex-marriage involves the contention that allowing same-sex marriage on the basis of a specific principle would require that, on the pain of inconsistency, we also accept polygamous marriage. This principle is typically some variant of the principle that a person should be able to marry any other person. Given that polygamous marriage is supposed to be bad, this would seem to entail that we should not allow same-sex marriage.

My first standard reply to this argument is that if different-sex marriage does not require us to accept polygamous marriage, then neither does accepting same-sex marriage. But, if accepting same-sex marriage entails that we have to accept polygamous marriage, the same would also apply to different-sex marriage. That this is so is shown by the following argument. If same-sex marriage is based on the principle that a person should be allowed to marry the person they wish to marry, then it would seem that different-sex marriage is based on the principle that a person should be allowed to marry the person of the opposite sex they wish to marry. By analogy, if allowing a person to marry any person they want to marry allows polygamous marriage, then allowing a person to marry a member of the opposite sex would also allow polygamous marriage-albeit only to a member of the opposite sex. But, if the slide to polygamy can be stopped in the case of different-sex marriage, then the same stopping mechanism can be used in the case of same-sex marriage.

In the case of different-sex marriage, there is generally an injunction against people marrying more than one person at a time. This same injunction would certainly seem to be applicable in the case of same-sex marriage. After all, there is nothing about accepting same-sex marriage that inherently requires accepting polygamous marriage.

In light of the above, the polygamy gambit against same-sex marriage would seem to fail. That is, the claim about the slide into polygamy that would supposedly result from legalizing same-sex marriage is unfounded.

There is, however, still an interesting question in regards to polygamy, namely the matter of whether or not it is wrong. After all, even if it could be shown that same-sex marriage would lead to polygamy, this would only be a problem is polygamy was actually wrong in some relevant way.

While polygamous marriage is not unheard of and there are also traditions of the practice, appealing to common practice or tradition to defend polygamy would obviously be fallacious. What is needed is a proper examination of the practice.

It is often the case that polygamy is condemned not directly because it is polygamy, but because of other factors associated with the specific sort of polygamy in question. For example, a culture that accepts polygamy might do so based on the view that women are inferior to men. In this case, it would not primarily be the polygamy that is problematic, but the way women are regarded and treated. As another example, polygamy might be practiced with under-aged and coerced brides (as has been seen in certain cults in the United States). In this case, the main concerns would seem to be with the coercion and age. In these and similar cases, the main point of concern would seem to not be that a man has many wives, but the treatment of the women. Thus, the moral problem with polygamy might not be a moral problem with the polygamy aspect, but the context of the polygamy.

Let it be supposed that polygamy was occurring in a situation devoid of such other negative factors. That is, those involved were not coerced, underage, or mistreated. The question would then be this: what is it about having multiple spouses itself that is wrong, if anything?

It might, obviously enough, be countered that any polygamous nature would be defective. For example, it could be argued that polygamy, by its very nature, must involve an imbalance in marital power (usually the male over the females) or, at the very least, it would always result in some of the spouses being denied the full benefits of marriage (that is, a single man could not attend to the emotional and physical needs of multiple women).

Naturally, it can easily be pointed out that critics of “traditional” marriage have pointed to the traditional imbalance in power between men and women and women being denied the full benefits of marriage. As such, these defects could be defects in marriage rather than a defect specific to polygamy-a polygamous marriage might merely multiple the disparities.

It is worth noting that these defects seem to arise from polygamy of the traditional sort: a male possessing a harem of wives. As such it would seem worthwhile to consider various forms of non-traditional polygamy, especially one involving multiple spouses of different sexes. Naturally, there could be different-sex polygamy of this sort (the marriage holds between the different sexes but not between the same sexes) or same-sex polygamy or bi-sexual polygamy. The notion of an extended marriage (with co-wives and co-husbands) was considered in science fiction by Robert Heinlein and he seemed to regard it as a potentially healthy and effective system of marriage. Of course, the fictional consideration of this matter could, at best, be considered a thought experiment. However, Heinlein did note the advantages for children (which he seemed to be regarded as of great importance in the context of marriage) in terms of the number of parents available to provide care and support.

Obviously enough, we have no real evidence of how a polygamous marriage between free and equal spouses would actually work-we just have our unfree and unequal world to draw upon for examples. However, it should, perhaps, not be dismissed out of hand or regarded as inherently defective.

In response to the obvious question, I would not want multiple wives. I failed with one wife and have no desire to multiply my failure.

One of the stock fallacious arguments against same sex-marriage is the slippery slope argument in which it is contended that allowing same sex-marriage will lead to allowing incestuous marriage. The mistake being made is, of course, that the link between the two is not actually made. Since the slippery slope fallacy is a fallacy, this is obviously a bad argument.

A non-fallacious argument that is also presented against same sex-marriage involves the contention that allowing same-sex marriage on the basis of a certain principle would require that, on the pain of inconsistency, we also accept incestuous marriage. This principle is typically some variant of the principle that a person should be able to marry any other person. Given that incestuous marriage is bad, this would seem to entail that we should not allow same-sex marriage.

My first standard reply to this argument is that if different-sex marriage does not require us to accept incestuous marriage, then neither does accepting same-sex marriage. But, if accepting same-sex marriage entails that we have to accept incestuous marriage, the same would also apply to different-sex marriage. That this is so is shown by the following argument. If same-sex marriage is based on the principle that a person should be allowed to marry the person they wish to marry, then it would seem that different-sex marriage is based on the principle that a person should be allowed to marry the person of the opposite sex they wish to marry. By analogy, if allowing a person to marry any person they want to marry allows incestuous marriage, then allowing a person to marry a member of the opposite sex would also allow incestuous marriage-albeit only to a member of the opposite sex. But, if the slide to incest can be stopped in the case of different-sex marriage, then the same stopping mechanism can be used in the case of same-sex marriage.

In the case of different-sex marriage, there is generally an injunction against people marrying close relatives. This same injunction would certainly seem to be applicable in the case of same-sex marriage. After all, there is nothing about accepting same-sex marriage that inherently requires accepting incestuous marriage.

One possible objection to my reply is that incestuous different-sex marriage is forbidden on the grounds that such relationships could produce children. More specifically, incestuous reproduction tends to be more likely to produce genetic defects which would provide a basis for a utilitarian moral argument against allowing incestuous marriage. Obviously, same-sex marriages have no possibility of producing children naturally. This would be a relevant difference between same-sex marriage and different-sex marriage. Thus, it could be claimed that while different-sex marriage can be defended from incestuous marriage on these grounds, the same can not be said for same-sex marriage. Once it is allowed, then it would be unprincipled to deny same-sex-incestuous marriage.

There are four obvious replies here.

First, if the only moral problem with incestuous marriage is the higher possibility of producing children with genetic defects, then incestuous same-sex marriage would not be morally problematic. Ironically, the relevant difference between the two that prevents denying same-sex-incestuous marriage would also make it morally acceptable.

Second, if a different-sex incestuous couple could not reproduce (due to natural or artificial sterility), then this principle would allow them to get married. After all, they are no more capable of producing children than a same-sex couple.

Third, if it could be shown that a different-sex incestuous couple would have the same chance of having healthy children as a non-incestuous couple, then this would allow them to get married. After all, they are no more likely to produce children with genetic defects than a non-incestuous couple.

Fourth, given that the principle is based on genetic defects being more likely than normal, it would follow that unrelated couples who are lkely to produce offspring with genetic defects should not be allowed to be married. After all, the principle is that couples who are likely to produce genetically defective offspring cannot be married. Thanks to advances in genetics, it is (or soon will be) possible (and affordable) to check the “genetic odds” for couples. As such, if incestuous marriage is wrong because of the higher possibility (whatever the level of unnacceptle risk might be) of genetic defects, then the union of unrelated people who have a higher possibiity of genetically defective children would also be wrong. This would seem to entail that if incestuous marriage should be illegal on these grounds, then so too should the union of unrelated people who have a similar chance of producing defective children.

In light of the above, the incest gambit against same-sex marriage would seem to fail. However, it also seems to follow that incestuous marriage would be acceptable in some cases.

Obviously enough, I have an emotional opposition to incest and believe that it should not be allowed. Of course, how I feel about it is no indication of its correctness or incorrectness. I do, of course, have argments against incest.

Many cases of incest involve a lack of consent, coercion or actual rape. Such cases often involve an older relative having sexual relations with a child. This sort of incest is clearly wrong and arguments for this are easy enough to provide-after all, one can make use of the usual arguments against coercion, child molestation and rape.

Where matters get rather more difficult is incest involving two consenting adults-be they of the same or different sexes. After all, the moral arguments that are based on a lack of consent no longer apply. Appealing to tradition will not work here-after all, that is a fallacy. The claim that it makes me uncomfortable or even sick would also not have any logical weight. As J.S. Mill argued, I have no right to prevent people from engaging in consenual activity just because I think it is offensive. What would be needed would be evidence of harm being done to others without their consent.

I have considered the idea that allowing incestuous marriage would be damaging to family relations. That is, the proper moral relations between relatives is such that incest would be harmful to the family as a whole. This is, obviously enough, analogous to the arguments made by those who oppose same-sex marriage. They argue that allowing same-sex marriage would be damaging to family relations because the proper moral relation between a married couple is such that same-sex marriage would damage to the family as a whole. As it stands, the evidence is that same-sex couples do not create such harm. Naturally, there is not much evidence involving incestuous marriages or relationships. However, if it could be shown that incestuous relationships between consenting adults were harmful, then they could thus be justly forbidden on utilitarian grounds. Naturally, the same would hold true of same-sex relationships.

Reflecting on incestuous marriage has, interestingly enough, given me some sympathy for people who have reflected on same-sex marriage and believe that there is something wrong about it. After all, I am against incestuous marriage and thinking of it makes me feel ill. However, I am at a loss for a truly compelling moral argument against it that would not also apply to non-related couples. My best argument, as I see it, is the harm argument. This is, as noted above, analogous to the harm argument used by opponents of same-sex marriage. The main difference is, of course, that the harm arguments presented by opponents of same sex-marriage have been shown to have premises that are not true. For example, claims about the alleged harms to children from having same-sex parents have been shown to be untrue. As such, I am not against same-sex marriage, but I am opposed to incestuous marriage-be it same or different sexes.

One stock “argument” against same-sex marriage is that legalizing it will put us on the slippery slope to bestiality. That is, if

(Photo credit: Wikipedia)

the Lone Ranger can marry Tonto, then he can marry Silver. This line of “reasoning” is easy enough to defeat.

First, this is an example of the classic slippery slope fallacy. Second, there is fact that if allowing different-sex marriage between humans does not lead to or warrant bestiality, then it would follow by analogy that allowing same-sex marriage between humans would not lead to or warrant bestiality. After all, if Adam marrying Eve does not warrant Adam marring a snake, then Adam marry Steve would not do so either.

While the bestiality argument is typically presented as a fallacious slippery slope, it is worth considering whether or not a proper argument can be presented that would show that allowing same-sex marriage entails that bestiality must also be accepted. Obviously, merely claiming that allowing same-sex marriage will lead to human-goat marriage is not enough. What would be needed would be logical reasons that we cannot accept same-sex marriage without being force by consistency to allow human-animal marriage.

Perhaps the most plausible way to argue for this is to begin by contending that same-sex marriage is justified by the principle that a person can marry anyone he wants to marry. This would, of course, justify same sex marriage: if a person can marry anyone he wants to marry, then he can marry another man. And a woman can marry another woman. It would also seem to justify human-animal marriage: if a person can marry anyone he wants, then he can marry a goat. As such, if we justify same-sex marriage on this principle, then it would also justify human-animal marriages. It would also justify human-rock marriages, human-iPad marriages and so on. A person could, on this principle, marry anything.

Now, if it is assumed that a person can marry anyone he wants, then this would also include marrying people who do not want to get married, people who are already married, and even Catholic nuns and priests.

Obviously enough, this principle leads to absurd results. As such, if this were the justifying principle for same-sex marriage, then there would be an excellent reason to reject same-sex marriage. However, if there is another principle (or principles) that would justify same-sex marriage while avoiding absurdity, then this principle could be sensibly used.

One obvious avenue of inquiry is to consider the principle that justifies different-sex marriage. While some might assume that different-sex marriage needs no justification, that would seem to beg the question. Naturally, if what justifies different-sex marriage would also apply to same-sex marriage, then there would not be a principled way to forbid one while accepting the other. However, if the justifying principle for different-sex marriage did not apply to same-sex marriage, then one could be allowed while the other is consistently forbidden.

One approach that people have taken is to argue that different-sex marriage is justified by a principle involving natural procreation. This principle would, obviously enough, not apply to same-sex marriage. However, this principle would lead to its own absurd results, namely that different-sex couples who could not have children or choose not to have children would not be permitted to marry. As such, unless we are willing to forbid such people from being married, then the procreation justification must be abandoned.

Once the procreation principle is out, there seem to be no non-ad hoc or non-question begging principles left that would allow different-sex marriage while forbidding same-sex marriage. For example, if a principle involving love is used, that could apply to different-sex and same-sex marriage (and, of course, we obviously do not take love to be a necessary condition for legal marriage). As another example, if someone claims that the principle is that men can only marry women, this would beg the question. It would be on par with arguing that mixed-race marriage is forbidden because the principle is that a person can only marry a person of the same ethnicity.

One worry at this point is that if any principle that warrants different-sex marriage would also warrant same-sex marriage, then it would seem that we would slide into human-animal marriage. Fortunately, this can be avoided in a principled manner.

Intuitively, marriage is a legal and moral agreement that requires the consent of both parties. Animals cannot, obviously enough, even understand marriage let alone provide consent. As such, a human cannot marry an animal. An animal can no more marry than it can make a promise or tell a lie. As such, same-sex marriage can be allowed without accepting a slide to human-animal marriage.

It might be countered that by taking marriage to require consent I am engaged in an ad hoc or question begging defense. After all, one might say, if marriage can include a man marrying a man, why can it not include a lack of consent and comprehension on the part of one partner, such as a goat? After all, if marriage is being redefined, why not redefine it completely?

The obvious reply is to note that if marriage can include a man marrying a woman, why can it not include a lack of consent and comprehension on the part of one partner, such as a goat? That is, if marriage is allowed, why not allow it for everyone and everything? However, if marriage (like debating or lying) requires certain capabilities (such as the ability to understand the relationship and consent to it), then humans can marry humans but not animals.

When I first heard that Irons spoke about a father marrying a son, I had inferred that he was just presenting the tired stock anti-same sex slippery slope fallacy in which it is claimed that if we allow same-sex marriage, then this will inevitably lead to allowing incest (and bestiality). The stock replies to this line of “reasoning” are to 1) point out that it is the slippery slope fallacy and 2) explain that allowing same-sex marriage no more allows incest (or bestiality) than does allowing different-sex marriage. After all, if different-sex couples can marry without a slide into different-sex incest and bestiality, then it would certainly seem to be the case that same-sex couples could marry without a slide into incest and bestiality.

However, Irons raised a more interesting point: if we allow same-sex marriage and this leads to allowing a father to marry his son, this could be used to work around the inheritance laws. After all, while a son would have to pay the inheritance tax on property he inherited from his father, he would not have to do so on property inherited from a deceased spouse. So, a father and son could get married not for the purpose of incest but for avoiding the inheritance tax. This idea might cause some confusion for certain Republicans—after all, this provides a way to avoid taxes but at the cost of allowing same-sex incestuous marriage.

While Irons did not explore all the ramifications, if anyone could marry anyone, then people could marry each other to get various spousal benefits (such as insurance coverage or green cards). While Irons’ point is interesting, it is easy enough to address these worries.

First, the claim that allowing same-sex marriage automatically entails that incestuous marriage be allowed is still the slippery slope fallacy. If accepting different-sex marriage does not warrant different sex-incest, then neither does same-sex marriage. And, of course, neither would warrant accepting bestiality. As such, there seems to be no reason to worry that legalizing same-sex marriage would lead to fathers marrying their sons to avoid taxes.

Second, while the idea of a father marrying a son to avoid taxes seems shocking, the general problem would be the exploitation of marriage. This is not a problem unique to same-sex marriage. After all, people already exploit different-sex marriage. As a specific example, a man could marry a woman (who is not too closely related) so she can avoid paying the inheritance task. Nothing about the current marriage laws forbids this. To make the more general point, any advantageous exploitation of marriage that would become available to a same-sex couple with the legalization of same-sex marriage is already available to different-sex couples.

If such advantageous exploitations are the problem, then the solution would be fixing these problems rather than focusing unfairly on the idea that same-sex couples would avail themselves of existing marital exploits. For example, if there is a terrible worry that people would engage in same-sex marriage to avoid the inheritance tax, then the solution would be to require spouses to pay this tax (or eliminate it altogether). As another example, if there is grave concern that two guys will get married just so one guy can get health insurance, then the solution is to change the insurance laws. After all, if the concern is that marriage will be exploited, then the clear solution is to take away the exploitable advantages—that way we can be sure people are not marrying just to avoid a tax, get insurance or for some other similar reason.

Some people do imply that same-sex couples would be more likely to engage in such advantageous exploits than different-sex couples or even that people would pretend to be gay to gain such advantages.

One obvious response is that there seems to be no reason to think that same-sex couples would be any more (or less) likely to marry for advantages. As far as people pretending to be gay, that seems to be rather odd—after all, a person who is not gay and wants to marry for an advantageous exploit could simply find a person of the opposite sex. The idea of pretending to be gay might make for a plot device for a comedy, but is hardly something that would be commonly (or even uncommonly) done.

If the problem is that same-sex couples would have the same advantages as different-sex couples, then this would seem to be a mere expression of prejudice.